In a heated skillet over medium heat, add a splash of oil and toss in the chopped onions. Cook for about 5-7 minutes until golden-brown, stirring occasionally to avoid burning. Add minced garlic and chipotle peppers, along with any desired spices and tomato paste. Stir for an additional 2 minutes until fragrant.

Stir in the canned black beans and vegetable stock, mashing lightly with a fork. Allow the mixture to simmer for about 5-8 minutes on low heat until it thickens and flavors meld. Finish with fresh lime juice.

To prepare corn tortillas, stack and wrap them in a damp paper towel. Microwave for approximately 30 seconds until warm and pliable.

On a greased baking sheet, lay out the warmed tortillas. Fill each with the black bean mixture, followed by cheese. Fold to create a pocket.

Preheat your oven to 400°F (200°C) and bake for about 15-20 minutes, until golden brown and crispy. Flip halfway through.

Allow the tacos to cool for a few minutes to enhance crispiness. Serve warm with toppings.